The following references will serve as background art for dosing dispensers and cakes of active ingredients used in combination therewith, and are incorporated herein by reference:
U.S. Pat. No. 4,171,546, Dirksing, issued Oct. 23, 1979; PA1 U.S. Pat. No. 4,208,747, Dirksing, issued June 24, 1980; PA1 U.S. Pat. No. 4,186,856, Dirksing, issued Feb. 5, 1980; PA1 U.S. Pat. No. 4,216,027, Wages, issued Aug. 5, 1980; PA1 U.S. Pat. No. 4,200,606, Kitko, issued Apr. 29, 1980; PA1 U.S. Pat. No. 4,248,827, Kitko, issued Feb. 3, 1981; PA1 U.S. Pat. No. 4,253,951, McCune, issued Mar. 3, 1981; PA1 U.S. Pat. No. 4,246,129, Kacher, issued Jan. 20, 1981; PA1 U.S. Pat. No. 4,251,012, Williams, issued Feb. 17, 1981; PA1 U.S. Pat. No. 4,247,070, Dirksing, issued Jan. 27, 1981; PA1 U.S. Pat. No. 4,302,350, Callicott, issued Nov. 24, 1981; PA1 U.S. Pat. No. 4,281,421, Nyguist et al., issued Aug. 4, 1981; PA1 U.S. Pat. No. 4,283,300, Kurtz, issued Aug. 11, 1981; PA1 U.S. Pat. No. 4,305,162, Cornelisse, Jr. et al., Dec. 15, 1981; PA1 U.S. Ser. No. 355,984, Mueller et al., filed Mar. 8, 1982; and European Pat. Appln. No. 0,005,286, Nyguist, published Nov. 14, 1979.
U.S. Pat. No. 3,154,495, Robson et al., issued Oct. 22, 1964, discloses articles comprising enveloped granular and small tableted hypochlorite materials.
A partially dissolving cake is disclosed in commonly owned U.S. Pat. No. 4,281,421, Nyquist, Kitko and Stradling, issued Aug. 4, 1981. The Nyquist et al. patent is directed to a partially insoluble cake comprising hypochlorite and metasilicate salts. One drawback to these cakes is that much of the hypochlorite is wasted. All of the cake is not immersed in liquid; just the lower part, and "leaching" will not dissolve the active located in the top part of the cake. Another drawback is substantial nonuniform delivery of the active.
U.S. Pat. No. 4,208,747, Dirksing, issued June 24, 1980, discloses highly effective dispensers which are placed in a toilet tank and which receive a dose volume of water from the toilet tank and dispense a dose volume of a solution of cleaning or disinfecting composition every time the toilet is flushed. This patent teaches that cake compositions can be used as the source of cleaning and disinfecting agents in such dispensers, but fails to address specific problems posed by certain types of cakes. One problem is that a cake of calcium hypochlorite material immersed completely in the dosing liquid tends to initially deliver excessively high levels of chlorine. Thus, the chlorine is used up too fast. FIGS. 9-14 and 18 of U.S. Pat. No. 4,208,747, Dirksing, disclose "top-feed" dispensers in which such cakes are completely immersed in the dosing liquid. There, the solution is drawn from above the cake. Such cake/dispenser combinations do not deliver a consistent amount of available chlorine over the life of the cake.
Dirksing also discloses a dosing dispenser of the "bottom-feed" type illustrated in FIGS. 1-8 and 15-17. Symmetrical rectangular-shaped cakes are used therein. In such dispensers the bleach cake is only partially immersed in dosing liquid in the reservoir. The solution is drawn from an area near the bottom of the cake.
U.S. Pat. No. 4,307,474, Choy, issued Dec. 29, 1981, discloses a passive dosing dispenser exhibiting improved resistance to gel clogging. An anti-clogging means comprising support means in the lowermost portion of the product chamber (cake compartment) and a level control means to control the level of liquid in the product chamber are also disclosed. The support means help to prevent gelled and solid chips from obstructing the flow of liquid in and out of the chamber.
Some major problems in this art have been with dissolving bleach cakes. One is dispensing even concentrations of the bleach. One cause of this is that particles from said cakes pass into the reservoir of the dispenser and thereby reduce the effective volume of liquid which is needed for rapid equilibrium and formation of the dosage of bleach which is to be dispensed in the next flush of the toilet. Further, the particles which break off the cake and pass through to the toilet water result in a loss of efficient bleach use, and some of the particles may clog the passageways through which liquid flows from the dispenser. Another problem has been that most of the effective volume of bleach liquid in the reservoir was dispensed with each dose. Yet another problem with some dispenser designs has been failure to dispense a full dose of bleach liquid each time.